NetVault Server: 9.2 Backup Device: Virtual Tape Library (VTL) attached to the NetVault Server and setup with shared drives (Client icons under each drive).
The VTL media is set to 'Read Only' for your benefit, as NetVault has found a problem backing up to certain VTL media (either the media itself i.e. the hard drive and/or connectivity to the hard drive). NetVault marks media as 'Read Only' when it has problems writing to the media.